Anti-PPAT monoclonal antibody Made to order

Background: Phosphopantetheine adenylyltransferase (PPAT) is a rate limiting enzyme which catalyzes the conversion of ATP and pantetheine to dephosphocoenzyme and pyrophosphate. The enzyme is allosteric in nature and regulated by Coenzyme A (CoA) through feedback inhibition. So far, several structures have been solved to decipher the catalytic mechanism of this enzyme. Methods: To address catalytic and inhibitory mechanisms of PPAT, structural insights from single crystal X-ray diffraction method were primarily used, followed by biophysical and biochemical analysis. Results: We have solved the structures of PPAT from Pseudomonas aeruginosa with its substrate analogue AMPPNP and inhibitor CoA. For the first time, a co-crystal structure of PPAT with Acetyl-CoA (AcCoA) was determined. Enzymatic analysis was performed to decipher the catalytic, allosteric and inhibitory mechanisms involved in regulation of PPAT. Binding affinities of PPAT with its substrates and inhibitors were determined by SPR. Conclusion: Previous studies from Escherichia coli and Arabidopsis indicated the inhibitory activity of AcCoA. PPAT-AcCoA structure along with some biochemical methods established AcCoA as an inhibitor to PPAT and illustrated its inhibitory mechanism. Transition from catalytic to allosteric state involves formation of ternary complex. We have studied the structural features of the ternary complex of PPAT along with its product pyrophosphate and inhibitor CoA and validated it with other biophysical and biochemical methods. Extensive analysis of all these 3D structures indicates that changes in side chains R90 and D94 are responsible for transition between catalytic and allosteric inhibitory states. General significance: These enzymatic studies provide new insights into the allosteric mechanism of PPAT. (C) 2016 Elsevier B.V. All rights reserved.

Phosphopantetheine adenylyltransferase (PPAT) has been recognized as a promising target to develop novel antimicrobial agents, which is a hexameric enzyme that catalyzes the penultimate step in coenzyme A biosynthesis. In this work, molecular modeling study was performed with a series of PPAT inhibitors using molecular docking, three-dimensional qualitative structure-activity relationship (3D-QSAR) and molecular dynamic (MD) simulations to reveal the structural determinants for their bioactivities. Molecular docking study was applied to understand the binding mode of PPAT with its inhibitors. Subsequently, 3D-QSAR model was constructed to find the features required for different substituents on the scaffolds. For the best comparative molecular field analysis (CoMFA) model, the Q(2) and R-2 values of which were calculated as 0.702 and 0.989, while they were calculated as 0.767 and 0.983 for the best comparative molecular similarity index analysis model. The statistical data verified the significance and accuracy of our 3D-QSAR models. Furthermore, MD simulations were carried out to evaluate the stability of the receptor-ligand contacts in physiological conditions, and the results were consistent with molecular docking studies and 3D-QSAR contour map analysis. Binding free energy was calculated with molecular mechanics generalized born surface area approach, the result of which coincided well with bioactivities and demonstrated that van der Waals accounted for the largest portion. Overall, our study provided a valuable insight for further research work on the recognition of potent PPAT inhibitors. Communicated by Ramaswamy H. Sarma